Loans, Leases, and Allowance for Credit Losses (Summary of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for loan and lease losses
Balance at beginning of period	$ 575	$ 513
Provision for loan losses	148	101	$ (258)
Gross loan and lease charge-offs	62	82
Recoveries	26	43
Net loan and lease charge-offs (recoveries)	36	39
Balance at ending of period	684	575	513
Reserve for unfunded lending commitments
Balance at beginning of period	61	40
Provision for unfunded lending commitments	(16)	21	(18)
Balance at end of period	45	61	40
Total allowance for credit losses	729	636
Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan and lease losses
Balance at beginning of period	572
Balance at ending of period		572
Cumulative Effect, Period of Adoption, Adjustment
Allowance for loan and lease losses
Balance at beginning of period	(3)
Balance at ending of period		(3)
Commercial
Allowance for loan and lease losses
Balance at beginning of period	300	311
Provision for loan losses	27	29
Gross loan and lease charge-offs	45	72
Recoveries	20	32
Net loan and lease charge-offs (recoveries)	25	40
Balance at ending of period	302	300	311
Reserve for unfunded lending commitments
Balance at beginning of period	16	19
Provision for unfunded lending commitments	3	(3)
Balance at end of period	19	16	19
Total allowance for credit losses	321	316
Commercial | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan and lease losses
Balance at beginning of period	300
Balance at ending of period		300
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Allowance for loan and lease losses
Balance at beginning of period	0
Balance at ending of period		0
Commercial real estate
Allowance for loan and lease losses
Balance at beginning of period	156	107
Provision for loan losses	92	49
Gross loan and lease charge-offs	3	0
Recoveries	0	0
Net loan and lease charge-offs (recoveries)	3	0
Balance at ending of period	241	156	107
Reserve for unfunded lending commitments
Balance at beginning of period	33	11
Provision for unfunded lending commitments	(16)	22
Balance at end of period	17	33	11
Total allowance for credit losses	258	189
Commercial real estate | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan and lease losses
Balance at beginning of period	152
Balance at ending of period		152
Commercial real estate | Cumulative Effect, Period of Adoption, Adjustment
Allowance for loan and lease losses
Balance at beginning of period	(4)
Balance at ending of period		(4)
Consumer
Allowance for loan and lease losses
Balance at beginning of period	119	95
Provision for loan losses	29	23
Gross loan and lease charge-offs	14	10
Recoveries	6	11
Net loan and lease charge-offs (recoveries)	8	(1)
Balance at ending of period	141	119	95
Reserve for unfunded lending commitments
Balance at beginning of period	12	10
Provision for unfunded lending commitments	(3)	2
Balance at end of period	9	12	$ 10
Total allowance for credit losses	150	131
Consumer | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for loan and lease losses
Balance at beginning of period	120
Balance at ending of period		120
Consumer | Cumulative Effect, Period of Adoption, Adjustment
Allowance for loan and lease losses
Balance at beginning of period	$ 1
Balance at ending of period		$ 1